The present invention relates to a process for producing 1,4-butanediol and, more in particular, it relates to a process for producing 1,4-butanediol, in which maleic acid anhydride and/or succinic acid anhydride are catalytically hydrogenated in a gas phase under the presence of a catalyst.
1,4-butanediol is a compound useful as starting material for polybutylene terephthalate resin, polyurethane resin, etc. Accordingly, there is a need for a process for producing 1,4-butanediol at reduced cost and increased efficiency.
The following processes for producing .gamma.-butyrolactone or 1,4-butanediol by catalytic hydrogenation of maleic acid anhydride and/or succinic acid anhydride or derivatives thereof have been disclosed.
(i) A process for producing .gamma.-butyrolactone in which maleic acid anhydride or succinic acid anhydride, etc. are catalytically hydrogenated in a gas phase by using a catalyst comprising zinc-copper-chromium (Japanese Patent Publication Sho 44-32567).
(ii) A process for producing .gamma.-butyrolactone in which maleic acid anhydride and/or succinic acid anhydride, etc. are catalytically hydrogenated in a gas phase under the presence of a reduction catalyst comprising copper oxide-beryllium oxide-zinc oxide (Japanese Patent Publication Sho 47-23294).
(iii) A process for producing .gamma.-butyrolactone in which maleic acid anhydride or succinic acid anhydride is hydrogenated in a liquid phase under the presence of a catalyst comprising nickel-molybdenum-barium and rhenium carried on a support Japanese Patent Laid-Open Sho 63-88044).
(iv) A process for producing 1,4-butanediol in which maleic acid anhydride and/or succinic acid anhydride, etc. are hydrogenated in a liquid phase under the presence of a catalyst containing elements belonging to sub-VII and sub-VIII groups or compounds thereof (Japanese Patent Laid-Open Sho 51-133212).
(v) A process for producing 1,4-butanediol in which maleic acid diester or fumaric acid diester, etc. are hydrogenatively decomposed in a gas phase in the presence of a copper chromite catalyst oxide-zinc oxide catalyst (Japanese Patent Application Sho 63-175062).
The processes of producing 1,4-butanediol which are disclosed above have a number of problems. For instance, in a process of catalytically hydrogenating maleic acid anhydride and/or succinic acid anhydride in a gas phase under the presence of a catalyst, many times only .gamma.-butyrolactone is formed instead of the desired 1,4-butanediol, except for the process proposed above by the present inventors. Further, the method of hydrogenating maleic acid anhydride and/or maleic acid in a liquid phase under the presence of a catalyst has a problem of requiring a high pressure of about 200 kg/cm.sup.2 and, thus requires an enormous installation cost and running cost. Further, although a process of hydrogenatively decomposing maleic acid diester, etc. in a gas phase under the presence of a catalyst does not require the high pressure described above, it still requires a step of diesterifying maleic acid anhydride, which makes the process extremely complicated. That is, since the reaction of converting a monoester into a diester is a equilibrium reaction, two reaction steps are required for sufficiently completing the reaction and it is necessary to add three reaction steps including the mono-esterifying step.
Further, a process for producing 1,4-butanediol by catalytic hydrogenation of maleic acid anhydride and/or succinic acid anhydride in a gas phase has not yet been known.
The present invention overcomes or at least mitigates the above-described problems of high installation cost and running cost and complicated processes for producing 1,4-butanediol from maleic acid anhydride and/or succinic acid anhydride.